With the development of information technology, especially with the popularization of cell phones, digital cameras, music players and other potable electronics, non-volatile memories have impacted many aspects of modern life. As a typical non-volatile memory, a flash memory has gained intensive development in past tens of years. When the semiconductor technology enters in a 22 nm technology node, the flash memory technology based on a floating-gate has encountered some difficulties. Therefore, phase change memories (PCMs) have become a hot topic of the non-volatile memories because of their superiorities in many aspects, such as unit area, writing/reading speed, writing/reading times, and data storage time.
FIG. 1 illustrates a structure of an existing PCM. The PCM includes a semiconductor substrate 100 containing semiconductor devices, or semiconductor devices and metal interconnection structures; a bottom electrode 101 leveling with one surface of the semiconductor substrate 100 and electrically connecting with the semiconductor devices or the metal interconnection structures in the semiconductor substrate 100; a first dielectric layer 102; a small electrode 103 with a cross section area smaller than a cross-section area of the bottom electrode 101 and electrically connecting with the bottom electrode 101 and leveling with one surface of the first dielectric layer 102; a phase change material layer 105 on the first dielectric layer 102; a transitional metal layer 106 having functions of adhesion and heat isolation on the phase change material layer 105; a top electrode 107 electrically connecting with an external circuit, and a second dielectric layer 104 covering the phase change material layer 105, the transitional metal layer 106 and the top electrode 107. The second dielectric layer 104 levels with one surface of the top electrode 107.
When a PCM is functioning, the semiconductor devices in the semiconductor substrate 100 supplies an electrical current, the electrical current flows through the bottom electrode 101, the small electrode 103, the phase change material layer 105, the transitional metal layer 106 and the top electrode 107, thus a joule heat is generated. The phase change material 105 is heated, which causes a phase change to happen in a portion of the phase change material 105 on the top of the small electrode 103, i.e., the crystal phase changes from crystalline to amorphous. The principle of the PCM is to use resistances of the crystalline state and the amorphous state to record data.
The phase change material 105 may need to be heated to a melting temperature and quenched to change the phase from crystalline to amorphous, thus a relatively larger current is required. Therefore, the power consumption of the existing PCMs is high. The disclosed methods and systems are directed to solve one or more problems set forth above and other problems.